Most creators don't save the audio from reels they like. That's leaving a tool on the floor.
Three workflows that actually use saved audio
1. Voice samples for sound design
If you make music, samples from reels (people laughing, kids in the background, ambient street audio) are royalty-free in the practical sense — find one, extract the MP3, drop it into your DAW, pitch-shift it, layer it under a beat. Some of the most-used samples in lo-fi this year started life as a 7-second reel.
2. Reference tracks for client work
When a client says "I want it to feel like that reel I sent you," pull the MP3 and analyze the BPM, key, and arrangement. Saves an hour of guessing.
3. Tutorial / explainer voice-over
Creators with a voice they like (a particular cadence, a regional accent, a specific energy) make great vocal reference for AI voice cloning tools. Extract once, generate variations, narrate your own videos in a voice that fits your brand.
What not to do
Don't re-upload someone's audio as your own original sound. Don't strip the audio off a reel and call it royalty-free. Don't sell content built on someone else's voice without permission. Personal use, references, sound design — fine. Re-publishing as yours — not fine.